Channels ▼
RSS

Good Vibrations: Translating Sound Waves to Vibrations



Lip reading is a critical means of communication for many deaf people, but it has a drawback: Certain consonants (for example, p and b) can be nearly impossible to distinguish by sight alone. Tactile devices, which translate sound waves into vibrations that can be felt by the skin, can help overcome that obstacle by conveying nuances of speech that can't be gleaned from lip reading.

Researchers in MIT's Sensory Communication Group are working on a new generation of such devices, which could be an important tool for deaf people who rely on lip reading and can't use or can't afford cochlear implants. The cost of the device and the surgery make cochlear implants prohibitive for many people, especially in developing countries.

"Most deaf people will not have access to that technology in our lifetime," said Ted Moallem, a graduate student working on the project. "Tactile devices can be several orders of magnitude cheaper than cochlear implants."

Moallem and Charlotte Reed, senior research scientist in MIT's Research Laboratory of Electronics and leader of the project, say the software they are developing could be compatible with current smart phones, allowing such devices to be transformed into unobtrusive tactile aids for the deaf.

"Anyone who has a smart phone already has much of what they would need to run the program," including a microphone, digital signal-processing capability, and a rudimentary vibration system, says Moallem.

Tactile devices translate sound waves into vibrations that allow the user to distinguish between vibratory patterns associated with different sound frequencies. The MIT researchers are testing devices that have at least two vibration ranges, one for high-frequency sounds and one for low-frequency sounds. Using such handheld devices, deaf people can more easily follow conversations than with lip reading alone, which requires a great deal of concentration, says Moallem.

"It's hard to have a casual conversation in a situation where you have to be paying attention like that," he says.

Current prototypes can be held in the user's hand or worn around the back of the neck, but once the acoustic processing software is developed, it could be easily incorporated into existing smart phones, according to the researchers. To lay the groundwork for such future applications, the researchers are investigating the best way to transform sound waves into vibrations.

Existing tactile aids have been in use for decades, but the MIT team hopes to improve the devices by refining the acoustic signal processing systems to provide tactile cues that are tailored to boost lip-reading performance, says Reed.

As part of their project, the researchers have done several studies on the frequency reception ability of the skin. The human ear can perceive frequencies up to 20,000 hertz, but for touch receptors in the skin, optimal frequencies are below 500 hertz. Using a laboratory setup with a device that can provide distinct vibration patterns to three fingers simultaneously, Moallem has done preliminary studies of deaf people's ability to interpret the vibrations from tactile devices. This project was originally inspired by earlier studies Reed did on the Tadoma technique, a communication method taught to deaf-blind people. Practitioners of that method hold their hands to someone's face while they are talking, allowing them to feel the vibrations of the face and neck. Reed's study, done about 20 years ago, showed that the deaf-blind subjects could successfully understand speech with this method -- especially if the other person spoke clearly and slowly.


Related Reading


More Insights






Currently we allow the following HTML tags in comments:

Single tags

These tags can be used alone and don't need an ending tag.

<br> Defines a single line break

<hr> Defines a horizontal line

Matching tags

These require an ending tag - e.g. <i>italic text</i>

<a> Defines an anchor

<b> Defines bold text

<big> Defines big text

<blockquote> Defines a long quotation

<caption> Defines a table caption

<cite> Defines a citation

<code> Defines computer code text

<em> Defines emphasized text

<fieldset> Defines a border around elements in a form

<h1> This is heading 1

<h2> This is heading 2

<h3> This is heading 3

<h4> This is heading 4

<h5> This is heading 5

<h6> This is heading 6

<i> Defines italic text

<p> Defines a paragraph

<pre> Defines preformatted text

<q> Defines a short quotation

<samp> Defines sample computer code text

<small> Defines small text

<span> Defines a section in a document

<s> Defines strikethrough text

<strike> Defines strikethrough text

<strong> Defines strong text

<sub> Defines subscripted text

<sup> Defines superscripted text

<u> Defines underlined text

Dr. Dobb's encourages readers to engage in spirited, healthy debate, including taking us to task. However, Dr. Dobb's moderates all comments posted to our site, and reserves the right to modify or remove any content that it determines to be derogatory, offensive, inflammatory, vulgar, irrelevant/off-topic, racist or obvious marketing or spam. Dr. Dobb's further reserves the right to disable the profile of any commenter participating in said activities.

 
Disqus Tips To upload an avatar photo, first complete your Disqus profile. | View the list of supported HTML tags you can use to style comments. | Please read our commenting policy.
 

Video